Let's say person A inflicts harm on person B.
Person C inflicts harm on person A and says he did so because A inflicted harm on B.
Can person D inflict harm on person C with the same reasoning? If he can, is it wrong to inflict harm on anyone?
If it's not wrong, then is C justifiable in his approach in harming A? If it's wrong, are C and D both wrong?
Added parts :
Person B had done no harm to person A.
All of this events happen with only two of these people together at a given time. That is, person A and B are together, or person A and C are together, or person C and D are together. Not more than 2.